Zombie ScienceThe book nearly implies without stating it outright that zombies violate Law of Conservation of Energy. Let's get serious here - zombies don't feel tired, they don't feel pain, they don't waste energy on all the functions necessary for long term survival of the body, so they can keep going far longer than a human, and it might seem to a naive observer that they can go forever, unless they rot away away.
This is of course a total nonsense, a captured zombie could be used to build a perpetual motion machine by just keeping in environment where body rot is unlikely. All zombies will run out of energy eventually. Assuming an average human is 80kg, 60% water, 20% body fat, 20% lean mass, and uses 2500kcal/day, that person will be left with literally not 1 gram of tissue in their body in 83 days. Even if we assume zombies can be far more efficient by shutting down nonessential body functions, a lot of this mass is still necessary for structural purposes. There's pretty much no way a zombie can remain active for more than a few months - not years like the author frequently claims.
A zombie could plausibly remain in a semi-dormant state for much longer, but visions of multi-year zombie sieges author sometimes draws need to be treated as fairy tales. If you can survive 3-6 months, you're basically saved.
The author makes other claims about zombies - that they're slow, clumsy, can't climb, can't throw things, can't use tools, can't coordinate, are not afraid or aware of fire and so on. These should be treated with caution. They might be true of a typical zombie, but how confident are you in risking your life on a bet that zombies you're facing are of the most vanilla variety? Different people had different abilities in life, and while zombification definitely generated massive brain damage, what was left might just be an exception. So prepare accordingly, but always have a backup plan just in case.
WeaponsIt's hard to describe advice about weapons given by the book as anything less than ridiculous. It's centered around use of silencers and long distance headshots. Both aspects are completely ridiculous.
Contrary to Hollywood portrayals, "silenced" weapons are still quite loud - and if zombies are attracted to slightest sound like the author portrays them to be (advising not even talking loudly just in case zombies might overhear that), any use of silencers is completely futile. And for untrained civilians able to reliably shoot a (even slowly) moving target in the head from long distance while shitting their pants? Such attempts are just the best way to waste all your ammunition.
Fortunately there are far more realistic solutions to the zombie menace - like shotguns. Sure, they are loud, but your chance of hitting zombie's head from a short to medium distance when your life is in danger is far better than with anything else unless you had years of training.
And contrary to author's claims, I would not completely ignore all targets except the head. Severed zombie head might be dangerous for a while, but your priority is survival, and it won't chase you. Mobility kill is good enough to save your life. Any hit that severs spinal column, shatters limb bones, breaks major muscles, and so on can ensure the zombie thus hit will not be following you. That's why grenades, molotovs, and all kinds of explosives are your friend. Of course the author is right - don't be stupid and approach the immobilized zombies, but your priority should be survival, not being a hero.
What to do if you have no firearms? If you had adequate training and quality equipment available, a polearm or a sword might be very viable - but let's be serious here, that's even less likely than sharpshooter training. If you have nothing better available, improvised spears are relatively easy to make, and can be adequate protection of last resort - they were used successfully for thousands of years against much bigger, stronger, and faster wild animal, than a stray zombie. Anything shorter like improvised knives and swords, baseball bats, hatchets, crowbars, and so on leads to far too great risk of infection even if you manage to eliminate the attacker, so only use in real desperate situations.
ArmorThe best thing you could possibly get, if your budget is unlimited is a shark suit. It costs about $5000 and protects from shark bites. Zombies have basically human anatomy, and any armor that protects you from sharks will also definitely protect you from zombies with a huge margin of safety.
If you don't have that kind of money to spare, or zombies caught you unprepared, you should still try to armor up. Any kind of motorcycle helmet and heavy leather clothing (of the kind bikers wear) will offer at least some degree of protection from zombie attack. It's not going to make you invulnerable of course, but every little helps.
Short Term Survival - Get on the RoofI feel the book covers that well - just get on the fucking roof, and get rid of the ladder. Zombies can't use ladders, can't climb, and even struggle with staircases, so heigh is your saviour.
I'd put much more trust in doors than the author. Plenty of doors are flimsy and will fall in minutes to even a single zombie, but depending on where you live, heavy fire doors routinely installed in all new buildings can stop zombies just as well as fires. Not forever perhaps, but your priority is not to die now. Time is on your side, and even if hundreds or thousands or zombies might be in the neighbourhood, they can't all try to break the doors at once due to physical constraints and zombies' lack of coordination.
Hopefully you'll only need to survive for a few days, and then help will come. But what if help doesn't arrive?
Medium Term Survival - Zombie DemographicsThe author inexplicably ignores demographics of zombies, but that's the key to your medium term survival. There are currently about 47 humans per square kilometer. Even in the worst kind of outbreak, where very few people survived, most will likely die without turning into zombies, and every day, significant percentage of zombies will die to delay, loss of energy, accidents, human resistance and so on. Within weeks their numbers will fall real low - even in apocalypse scenario after 3 months it's difficult to imagine more than 1 zombie per square kilometer worldwide, falling to maybe 0.1 per square kilometer after 3 more months.
So what do you need to do? Get the hell out of the city. A single zombie or a handful is not very dangerous, and in the countryside that's the most you're likely to encounter. It's only in densely populated urban areas where you're likely to find literal hordes.
In apocalypse scenario, you won't really have to worry about food and supplies - zombie numbers are falling rapidly, and any store will have huge amounts of nonperishable food for the few survivors. Store trips are extremely dangerous places in the first days of the outbreak, especially for stores located in more populated areas, but a couple weeks or months in, in broad daylight, with prior reconnaissance and cleanup of the surroundings, it's manageable level of risk.
Long Term Survival - Rebuilding HumanityIt's exceedingly unlikely that any kind of outbreak would get all of humanity - most likely it will be geographically isolated and even if a large region falls to the zombies, the military will soon intervene (hopefully not with weapons of mass destruction or carpet bombing), and thing will go back to normal before a year passes.
Still, if we're considering apocalypse scenarios, we might as well consider the worst case of all.
And here the author goes completely off base - recommending setting up the new society for your group in tho most inhospitable environment possible - like deep Siberia, or a desert, or even a jungle. That's just insane. Zombie numbers will be falling rapidly, so your first problem is shifting from eating non-perishable pre-apocalypse food to growing new food - and for that you'll need either coastline for fishing, pastures for livestock, or decent arable land (wildlife hunting can supplement your food, but it's unlikely to work as its primary source) - it won't give the yields modern agriculture, but then the number of survivors will be much less than seven billion.
Bandits are a risk of course, but people can and will defend their homes, and bandits won't last very long in such an environment, just like they didn't in ancient times. Historically, small scale bandits mostly robbed travellers, not farms - you need a small army to setup a successful long term farm robbing operation, and if you have an army you might just as well call yourself President for life, wipe out all other bandits, and start collecting taxes. Of course history doesn't reliably tell what might happen to the society after a catastrophic zombie outbreak, but it very reliably predicts what's going to happen if a bunch of fat urbanites try to set up new life in environment where even natives living there for generations can barely make ends meet.
It's still far safer to deal with some potential bandits than with near certain starvation.